Improve sparse datapoint plotting in pyqtgraph and fastplotlib #24

Job	Run time
build-linux (ubuntu-24.04, x86_64, ubuntu24, linux-ubuntu24)	3m 11s
build-linux (ubuntu-24.04-arm, arm64, ubuntu24, linux-ubuntu24)	2m 40s
build-linux (ubuntu-22.04, x86_64, ubuntu22, linux-ubuntu22)	3m 3s
	8m 54s

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